Manufacturing method of active matrix substrate, active matrix substrate and liquid crystal display device

ABSTRACT

A method of manufacturing an active matrix substrate is provided that uses a technique of transferring a thin film device. In forming thin film transistors and pixel electrodes on an original substrate before transfer, an insulator film such as an interlayer insulation film or the like, is previously removed before the pixel electrodes are formed. Further, the original substrate is separated by exfoliation to transfer the device to a transfer material to cause the pixel electrodes to partially appear in the surface or the vicinity of the surface of the device. This portion permits application of a voltage to a liquid crystal through the pixel electrode.

This is one of two ( 2 ) reissue applications directed to variousaspects of manufacturing method of active matrix substrate, activematrix substrate and liquid crystal display device described in U.S.Pat. No. 6,127,199. The first reissue application is application Ser.No. 10/263,070, filed Oct. 3, 2002. The second reissue application isthe present application, which is a Divisional of application Ser. No.10/263,070. As noted above, this is a Divisional of application Ser. No.10/263,070, filed Oct. 3, 2002 now Re. 38,466 which is a reissue of U.S.Pat. No. 6,127,199, which corresponds to U.S. patent application Ser.No. 09/113,373 filed Jul. 10, 1998, which is a Continuation-In-Part ofApplication No. PCT/JP97/04110 filed Nov. 11, 1997.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-Part of international applicationPCT/JP97/04110, filed on Nov. 11, 1997, which claims priority fromJapanese application Nos. 8-315590 and 8-327688, filed on Nov. 12, 1996and Nov. 22, 1996, respectively. PCT/JP97/04110 and Japanese applicationNos. 8-315590 and 8-327688 are incorporated by reference herein in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing an activematrix substrate using a method of transferring a thin film device. Thepresent invention also relates to an active matrix substratemanufactured by the manufacturing method, and a liquid crystal displaydevice comprising this active matrix substrate as one of a pair ofsubstrates.

2. Description of Related Art

For example, a liquid crystal display using thin film transistors (TFT)is manufactured through the step of forming thin film transistors on asubstrate by CVD or the like. Since the step of forming thin filmtransistors on the substrate is accompanied with high temperatureprocessing, it is necessary to use material for the substrate which hasexcellent heat resistance, i.e., material having a high softening pointand melting point. At present, silica glass is used as a substrate whichcan resist a temperature of about 10000C, and heat resistant glass isused as a substrate which can resist a temperature of about 500° C.

Namely, the substrate on which thin film elements are mounted mustsatisfy conditions for producing the thin film transistors. Therefore,the substrate used is determined so as to satisfy conditions formanufacturing a device to be mounted thereon.

However, in consideration of only the steps after the substratecomprising the thin film transistors such as TFT or the like mountedthereon is completed, in some cases, the above-described substrate isnot always satisfactory.

For example, in the above-described manufacturing process accompaniedwith high temperature processing, a quartz substrate, a heat-resistantsubstrate, or the like is used. However, these substrates are veryexpensive, and thus cause an increase in product cost.

Also the glass substrate has the properties that it is heavy and easilybroken. A liquid crystal display used for portable electronic apparatussuch as a palm top computer, a portable telephone, etc. is preferablylight weight, can resist a little deformation, and is hardly broken bydropping. However, in fact, the glass substrate is generally heavy, lessresistant to deformation and is possibly broken by dropping.

In other words, there are gaps between the limitations caused bymanufacturing conditions and preferable characteristics required forproducts, and it is very difficult to satisfy the conditions andcharacteristics.

SUMMARY OF THE INVENTION

The present invention has been achieved in consideration of theseproblems, and an object of the invention is to provide a novel techniquewhich permits independent free selection of a substrate used inproducing thin film devices, and a substrate (a substrate havingpreferable properties for application of a product) used in, forexample, actual use of a product, and a completely new method ofeffectively manufacturing an active matrix substrate having excellentproperties and a liquid crystal display device by using the technique.

In order to achieve the object, the present invention may include thefollowing.

(1) The present invention provides a method of manufacturing an activematrix substrate comprising a pixel portion including thin filmtransistors connected to scanning lines and signal lines arranged in amatrix, and pixel electrodes respectively connected to terminals of thethin film transistors, the method may include:

-   -   forming a separation layer on the substrate;    -   forming the thin film transistors over the separation layer;    -   forming an insulation film on the thin film transistors and over        the separation layer;    -   selectively removing at least a portion of the insulation film        in a region where each of the pixel electrodes is to be formed;    -   forming each of the pixel electrodes on the insulation film and        the separation layer in a region where at least a portion of the        insulation film has been removed;    -   adhering the thin film transistors to a transfer material with        an adhesive layer    -   producing exfoliation in the separation layer and/or at an        interface of the separation layer and the substrate to separate        the substrate from the separation layer; and    -   removing any portion of the separation layer remaining on the        pixel electrodes and under the insulation film to form an active        matrix substrate using the transfer material as a new substrate.

In the method of manufacturing an active matrix substrate of the presentinvention, the thin film transistors and the pixel electrodes formed onthe substrate are transferred to the desired transfer material by thedevice transfer technique developed by the applicant of the presentinvention. In this case, the device transferred onto the transfermaterial is reverse to a normal device. In the transferred device,consequently, the pixel electrode is covered with the insulator layersuch as an interlayer insulation film or the like before transfer. Ifthe insulation film has a large thickness, a large voltage loss occursin this portion, and thus a sufficient voltage cannot be applied to aliquid crystal.

Therefore, in the manufacturing method of the present invention, informing the thin film transistors and pixel electrodes on the originalsubstrate before transfer, at least a portion of the insulator layersuch as the interlayer insulation film or the like is removed before thepixel electrodes are formed. In this case, the entire insulator layer ispreferably removed. However, when the insulation film remainingunremoved is thin, at least a portion of the insulator layer may beremoved because no problem occurs in application of a voltage to theliquid crystal.

In any case, by separating the original substrate after a device istransferred onto the transfer material, the pixel electrode partiallyappears at least in the vicinity of the surface of the device.Therefore, a sufficient voltage can be applied to the liquid crystallayer from this portion.

The insulation film remaining on the pixel electrodes can also beseparately removed in another step (for example, in a step aftertransfer of the device).

(2) The present invention provides a method of manufacturing an activematrix substrate comprising a pixel portion including thin filmtransistors connected to scanning lines and signal lines arranged in amatrix, and pixel electrodes respectively connected to terminals of thethin film transistors, and the method may include:

-   -   forming a separation layer on a substrate;    -   forming an intermediate layer on the separation layer;    -   forming the thin film transistors on the intermediate layer;    -   forming an insulation film on the thin film transistors and the        intermediate layer;    -   selectively removing a portion of the insulation film in a        region where each of the pixel electrodes is to be formed;    -   forming each of the pixel electrodes on the insulation film and        the separation layer in the region where at least a portion of        the insulation film is removed;    -   adhering the thin film transistors to a transfer material with        an adhesive layer;    -   producing exfoliation in the separation layer and/or at an        interface of the separation layer and the substrate to separate        the substrate from the separation layer; and    -   removing any portion of the separation layer remaining on the        intermediate layer and the pixel electrodes to form an active        matrix substrate using the transfer material as a new substrate.

This invention is different from invention (1) in that the intermediatelayer is provided. The intermediate layer can comprise a single layerfilm of an insulator, such as an SiO₂ film or the like, or amultilayered film comprising a laminate of an insulator and a metal. Theintermediate layer functions to facilitate separation from theseparation layer, protect the transistors from contamination duringremoval of the separation layer, ensure insulation properties of thetransistors, and suppress irradiation of the transistors with laserlight.

In forming the thin film transistors and the pixel electrodes on theoriginal substrate before transfer, at least a portion of the insulatorlayer such as an interlayer insulation film or the like, which causes aproblem in the later steps, is removed before the pixel electrodes areformed. In this case, the whole insulation film and intermediate layerbelow it are preferably removed at the same time from the viewpoint ofprevention of a loss of the voltage applied to the liquid crystal.However, where the insulator layer remaining unremoved is thin, asufficient voltage can be applied to the liquid crystal from the pixelelectrodes. Therefore, at least a portion of the insulation film may beremoved.

In the present invention, by separating the original substrate after adevice is transferred to the transfer material, the pixel electrodepartially appears at least in the vicinity of the surface of the device.Therefore, a voltage can sufficiently be applied to the liquid crystallayer from this portion.

The insulation film remaining on the pixel electrodes can separately beremoved in another step (for example, the step after transfer of thedevice).

(3) In invention (2), at least a portion of the insulation film may beselectively removed in the step of forming contact holes forelectrically connecting the pixel electrodes to the thin filmtransistors. Since the same manufacturing step is used for bothpurposes, an increase in the number of the manufacturing steps can beprevented.(4) In invention (3), the contact holes may be used for connecting thepixel electrodes directly to an impurity layer which constitutes thethin film transistors.

Namely, in a structure in which the pixel electrodes are connecteddirectly to terminals(source layer or drain layer) of the thin filmtransistors, the insulator layer such as an interlayer insulation filmor the like may be removed in formation of the contact holes forconnection.

(5) In invention (3), the contact holes may be used for connecting thepixel electrodes to respective electrodes connected to an impurity layerwhich constitutes the thin film transistors.

Namely, in a structure in which the pixel electrodes are connected toterminals(the source layer or drain layer) of the thin film transistorsthrough electrodes made of a metal or the like (when the pixelelectrodes are in a layer above the electrodes of the transistors), theinsulator layer such as an interlayer insulation film or the like may beremoved in formation of the contact holes for connection.

(6) In any one of inventions (1) to (5), at least one of a color filterand a light shielding film may be after the step of forming the pixelelectrodes.

In the structure of normal thin film transistors, if the color filter orthe light shielding film is formed on the pixel electrodes, applicationof a voltage to the liquid crystal layer from the pixel electrodes isinterfered with, and thus such a structure cannot be used.

However, in the present invention, a device is reversed by transfer, andthus the region where a voltage is applied to the liquid crystal layerfrom the pixel electrode is formed on the side (i.e., the thin filmtransistor side) opposite to a conventional device. Therefore, even ifthe color filter or the light shielding film has been previously formedon the original substrate before transfer, no trouble occurs. In thiscase, only common electrodes may be formed on the opposite substrate,and the color filter or the light shielding film, which isconventionally formed on the opposite substrate, need not be strictlyaligned with the pixel electrodes, thereby facilitating assembly of aliquid crystal display device.

(7) In any one of inventions (1) to (6), in selectively removing atleast a portion of the insulation film, at least a portion of theinsulation film may be selectively removed in a region where an externalconnection terminal is to be provided.

In an active matrix substrate, where the external connection terminal(for example, a terminal for connecting a liquid crystal driving IC) isrequired, this terminal also must be at a position near at least thesurface of the device.

Therefore, in the region where the external connection terminal isprovided, the insulator film such as an interlayer insulation film orthe like is removed. In this case, the under insulation film(intermediate layer) must be removed in the same step or a differentstep.

(8) In invention (7), in the region where at least a portion of theinsulation film is selectively removed for providing the externalconnection terminal, a conductive layer formed from the same material asthe pixel electrodes or an electrode connected to an impurity layerwhich constitutes the thin film transistors may be formed. In thisinvention, the conductive layer may be used for forming the externalconnection terminal.(9) The present invention also may provide a method of manufacturing anactive matrix substrate having a pixel portion including thin filmtransistors connected to scanning lines and signal lines arranged in amatrix, and pixel electrodes connected to terminals of the thin filmtransistors, and the method may include:

-   -   forming a separation layer on a transmissive substrate;    -   forming the thin film transistors over the separation layer or        on a predetermined intermediate layer formed on the separation        layer;    -   forming an insulation film on the thin film transistors;    -   forming the pixel electrodes comprising a transparent conductive        material on the insulation film;    -   forming a light shielding layer that is overlapped with the thin        film transistors and is not overlapped with at least a portion        of the pixel electrodes;    -   adhering the thin film transistors and the light shielding layer        on a transmissive transfer material with a transmissive adhesive        layer;    -   irradiating the separation layer with light through the        transmissive substrate to produce exfoliation in the separation        layer and/or at an interface of the separation layer and the        transmissive substrate to separate the transmissive substrate        from the separation layer;    -   forming a photoresist on a surface from which the transmissive        substrate is separated, or on the surface of a layer which        appears after removing any remaining portion of the separation        layer;    -   irradiating light to expose only a predetermined portion of the        photoresist using the light shielding layer as a mask, followed        by development to form a desired photoresist mask;    -   selectively removing at least a portion of the intermediate        layer and the insulation film or at least a portion of the        insulation film using the photoresist mask; and    -   removing the photoresist mask to form an active matrix substrate        using the transfer material as a new substrate.

Although, in inventions (1) to (8), at least a portion of the insulatorlayer below the pixel electrodes may be removed before transfer, in thisinvention, at least a portion of the insulator layer below the pixelelectrodes may be removed in a self alignment manner using the lightshielding film after transfer.

Namely, the light shielding layer may be formed on the originalsubstrate before transfer, and may be used as an exposure mask aftertransfer to form a desired resist pattern by utilizing the fact that thelight shielding layer is formed around the pixel electrodes. Then, atleast a portion of the insulator layer below the pixel electrodes may beremoved by using the resist pattern as an etching mask.

(10) This invention provides a method of manufacturing an active matrixsubstrate having a pixel portion including thin film transistorsconnected to scanning lines and signal lines arranged in a matrix, andpixel electrodes respectively connected to terminals of the thin filmtransistors, and the method may include:

-   -   forming a separation layer on a substrate;    -   forming the pixel electrodes over the separation layer or on a        predetermined intermediate layer formed on the separation layer;    -   forming an insulation film on the pixel electrodes, forming the        thin film transistors on the insulation film, and respectively        connecting the thin film transistors to the pixel electrodes;    -   adhering the thin film transistors to a transfer material with        an adhesive layer;    -   producing exfoliation in the separation layer and/or at an        interface of the separation layer and the substrate to separate        the substrate from the separation layer; and    -   removing any portion of the separation layer remaining on the        intermediate layer to form an active matrix substrate using the        transfer material as a new substrate.

In this invention, when the thin film transistors are formed on theoriginal substrate before transfer, the pixel electrodes are previouslyformed. The original substrate before transfer is separated aftertransfer to automatically expose the surfaces of the pixel electrodes orposition the pixel electrodes at least at the surface of the device.

(11) In invention (10), a conductive material layer may be formed on theseparation layer or on the intermediate layer at a position where anexternal connection terminal is to be formed.

When the thin film transistors are formed on the original substratebefore transfer, the conductive material layer for forming the externalconnection terminal is previously formed as well as the pixel electrode.The original substrate before transfer is separated after transfer toautomatically expose the surface of the conductive material layer at thesame time as the pixel electrodes, or position the conductive materiallayer near the surface, leaving the intermediate layer. In the lattercase, the intermediate layer is removed in the same step or a differentstep to expose the surface of the conductive material layer. Theconductive material layer with the exposed surface serves as theexternal connection terminal.

(12) This invention provides an active matrix substrate manufactured bythe method of manufacturing an active matrix substrate of any one ofinventions (1) to (11). Since limitations due to the manufacturingconditions are eliminated so that the substrate can freely be selected,a novel active matrix substrate, which has not yet been realized, can berealized.(13) This invention provides a liquid crystal display device comprisingan active matrix substrate manufactured by the method of manufacturingan active matrix substrate of any one of inventions (1) to (11). Forexample, it is possible to realize an active matrix type liquid crystaldisplay device comprising a plastic substrate and having flexibility.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing the first step of a method oftransferring a thin film element.

FIG. 2 is a sectional view showing the second step of a method oftransferring a thin film element.

FIG. 3 is a sectional view showing the third step of a method oftransferring a thin film element.

FIG. 4 is a sectional view showing the fourth step of a method oftransferring a thin film element.

FIG. 5 is a sectional view showing the fifth step of a method oftransferring a thin film element.

FIG. 6 is a sectional view showing the sixth step of a method oftransferring a thin film element.

FIG. 7 is a drawing illustrating the whole configuration of a liquidcrystal display device.

FIG. 8 is a drawing illustrating the configuration of a principalportion of a liquid crystal display device.

FIG. 9 is a sectional view illustrating the structure of a principalportion of a liquid crystal display device.

FIG. 10 is a sectional view showing the first step of a method ofmanufacturing an active matrix substrate in accordance with a firstembodiment of the present invention.

FIG. 11 is a sectional view showing the second step of the method ofmanufacturing an active matrix substrate in accordance with the firstembodiment of the present invention.

FIG. 12 is a sectional view showing the third step of the method ofmanufacturing an active matrix substrate in accordance with the firstembodiment of the present invention.

FIG. 13 is a sectional view showing the fourth step of the method ofmanufacturing an active matrix substrate in accordance with the firstembodiment of the present invention.

FIG. 14 is a sectional view showing the fifth step of the method ofmanufacturing an active matrix substrate in accordance with the firstembodiment of the present invention.

FIG. 15 is a sectional view showing the first step of a method ofmanufacturing an active matrix substrate in accordance with a modifiedembodiment of the first embodiment.

FIG. 16 is a sectional view showing the second step of the method ofmanufacturing an active matrix substrate in accordance with the modifiedembodiment of the first embodiment.

FIG. 17 is a sectional view showing the third step of the method ofmanufacturing an active matrix substrate in accordance with the modifiedembodiment of the first embodiment.

FIG. 18 is a sectional view showing the first step of a method ofmanufacturing an active matrix substrate in accordance with a secondembodiment of the present invention.

FIG. 19 is a sectional view showing the second step of the method ofmanufacturing an active matrix substrate in accordance with the secondembodiment of the present invention.

FIG. 20 is a sectional view showing the structure of a principal portionof a liquid crystal display device in accordance with a third embodimentof the present invention.

FIG. 21 is a drawing showing electrical connection in the liquid crystaldisplay device shown in FIG. 20.

FIG. 22 is a sectional view showing the first step of a method ofmanufacturing an active matrix substrate in accordance with the thirdembodiment of the present invention.

FIG. 23 is a sectional view showing the second step of the method ofmanufacturing an active matrix substrate in accordance with the thirdembodiment of the present invention.

FIG. 24 is a sectional view showing the third step of the method ofmanufacturing an active matrix substrate in accordance with the thirdembodiment of the present invention.

FIG. 25 is a sectional view showing the fourth step of the method ofmanufacturing an active matrix substrate in accordance with the thirdembodiment of the present invention.

FIG. 26 is a sectional view showing the fifth step of the method ofmanufacturing an active matrix substrate in accordance with the thirdembodiment of the present invention.

FIG. 27 is a sectional view showing the sixth step of the method ofmanufacturing an active matrix substrate in accordance with the thirdembodiment of the present invention.

FIG. 28 is a sectional view showing the first step of a method ofmanufacturing an active matrix substrate in accordance with a modifiedembodiment of the third embodiment.

FIG. 29 is a sectional view showing the second step of the method ofmanufacturing an active matrix substrate in accordance with the modifiedembodiment of the third embodiment.

FIG. 30 is a sectional view showing the third step of the method ofmanufacturing an active matrix substrate in accordance with the modifiedembodiment of the third embodiment.

FIG. 31 is a sectional view showing the first step of a method ofmanufacturing an active matrix substrate in accordance with a fourthembodiment of the present invention.

FIG. 32 is a sectional view showing the second step of the method ofmanufacturing an active matrix substrate in accordance with the fourthembodiment of the present invention.

FIG. 33 is a sectional view showing the third step of the method ofmanufacturing an active matrix substrate in accordance with the fourthembodiment of the present invention.

FIG. 34 is a sectional view showing the fourth step of the method ofmanufacturing an active matrix substrate in accordance with the fourthembodiment of the present invention.

FIG. 35 is a sectional view showing the fifth step of the method ofmanufacturing an active matrix substrate in accordance with the fourthembodiment of the present invention.

FIG. 36 is a sectional view showing the sixth step of the method ofmanufacturing an active matrix substrate in accordance with the fourthembodiment of the present invention.

FIG. 37 is a sectional view showing the seventh step of the method ofmanufacturing an active matrix substrate in accordance with the fourthembodiment of the present invention.

FIG. 38 is a sectional view of a liquid crystal display device inaccordance with the fourth embodiment of the present invention.

FIG. 39 is a sectional view showing the first step of a method ofmanufacturing an active matrix substrate in accordance with a fifthembodiment of the present invention.

FIG. 40 is a sectional view showing the second step of the method ofmanufacturing an active matrix substrate in accordance with the fifthembodiment of the present invention.

FIG. 41 is a sectional view showing the third step of the method ofmanufacturing an active matrix substrate in accordance with the fifthembodiment of the present invention.

FIG. 42 is a sectional view of a liquid crystal display device inaccordance with the fifth embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An exfoliating method in accordance with an embodiment of the presentinvention is described in detail below with reference to the attacheddrawings.

In the present invention, an active matrix substrate is formed by using“the device transfer technique” developed by the applicant of thisinvention. Therefore, the contents of “the device transfer technique”are first described.

(Contents of device transfer technique)

FIGS. 1 to 6 are drawings illustrating the contents of the devicetransfer technique.

[Step 1]

As shown in FIG. 1, a separation layer (light absorbing layer) 120 isformed on a substrate 100.

The substrate 100 and the separation layer 120 are described.

(1) Description of the substrate 100

The substrate 100 preferably has transmissivity which allowstransmission of light. In this case, the light transmittance ispreferably 10% or more, and more preferably 50% or more. With too lowtransmittance, attenuation (loss) of light is increased, and thus alarge quantity of light is required for exfoliating the separation layer120.

Also the substrate 100 is preferably made of a material having highreliability, particularly a material having excellent heat resistance.The reason for this is that for example, when a transferred layer 140 oran intermediate layer 142, which will be described below, are formed,the process temperature is sometimes increased (for example, about 350to 1000° C.) according to the type and the forming method. However, inthis case, in forming the transferred layer 140 or the like on thesubstrate 100 having excellent heat resistance, the ranges of the filmforming conditions such as the temperature condition, etc. are widened.

Therefore, if the highest temperature in formation of the transferredlayer 140 is Tmax, the substrate 100 is preferably made of a materialhaving a strain point higher than Tmax. Specifically, the material forforming the substrate 100 preferably has a strain point of 350° C. orhigher, more preferably 500° C. or higher. Examples of such materialsinclude heat resistant glass such as quartz glass, Corning 7059, NihonDenki glass OA-2, and the like Although the thickness of the substrate100 is not limited, the thickness is preferably about 0.1 to 5.0 mm,more preferably about 0.5 to 1.5 mm. With the substrate 100 having anexcessively small thickness, the strength deteriorates, and with thesubstrate 100 having an excessively large thickness, attenuation oflight easily occurs when the substrate 100 exhibits low transmittance.When the substrate 100 exhibits high transmittance, the thicknessthereof may exceed the upper limit. In order to permit uniformirradiation, the substrate 100 preferably has a uniform thickness.

(2) Description of the separation layer 120

The separation layer 120 has the property of absorbing light to produceexfoliation in the layer and/or the interface thereof (referred to as“internal exfoliation” and “interfacial exfoliation” hereinafter), andpreferably, the adhering strength between the atoms or molecules of thematerial which constitutes the separation layer 120 is reduced oreliminated by irradiation of light, i.e., internal exfoliation and/orinterfacial exfoliation results from ablation.

Further, in some cases, gases are discharged from the separation layer120 by irradiation of light to cause a separating effect. Namely, thecomponents contained in the separation layer 120 are discharged asgases, or the separation layer 120 absorbs light to become a gas for amoment and the vapor is discharged to contribute to separation. Examplesof the composition of the separation layer 120 include the following Ato E.

A. Amorphous silicon (a-Si)

Amorphous silicon may contain hydrogen (H). In this case, the H contentis preferably about 2 atomic % or more, more preferably about 2 to 20atomic %. When a predetermined amount of hydrogen (H) is present,hydrogen is discharged by irradiation of light to generate internalpressure in the separation layer 120, which serves as the force toexfoliate upper and lower thin films. The content of hydrogen (H) inamorphous silicon can be adjusted by appropriately setting filmdeposition conditions, e.g., the gas composition, gas pressure, gasatmosphere, gas flow rate, temperature, substrate temperature, inputpower, etc. of CVD.

B. Various oxide ceramics such as silicon oxide or silicates, titaniumoxide or titanates, zirconium oxide or zirconates, lanthanum oxide orlanthanates, and the like, dielectric material (ferroelectric material)or semiconductor.

Examples of silicon oxides include SiO, SiO₂ and Si₃O₂, and examples ofsilicate compounds include K₂SiO₃, Li₂SiO₃, CaSiO₃, ZrSiO₄, and Na₂SiO₃.

Examples of titanium oxides include Tio, Ti₂O₃ and TiO₂, and examples oftitanate compounds include BaTiO₄, BaTiO₃, Ba₂Ti₉O₂₀, BaTi₅O₁l, CaTiO₃,SrTiO₃, PbTiO₃, MgTiO₃, ZrTiO₂, SnTiO₄, Al₂TiO₅, and FeTiO₃.

Zirconium oxide is ZrO₂, and examples of zirconate compounds includeBaZrO₃, ZrSiO₄, PbZrO₃, MgZrO₃, and K₂ZrO₃.

C. Ceramics such as PZT, PLZT, PLLZT, PBZT and the like, or dielectricmaterial (ferroelectric material)

D. Nitride ceramics such as silicon nitride, aluminum nitride, titaniumnitride, and the like.

E. Organic polymer material

As an organic polymer material, any material having bonds such as —CH—,—CO— (ketone), —CONH— (amido), —NH— (imido), COO— (ester), —N═N— (azo),—CH═N— (Schiff) or the like (these bonds are cut by light irradiation),particularly any material having many bonds of such a type can be used.The organic polymer material may have an aromatic hydrocarbon (at leastone benzene ring or condensed ring thereof) in the composition thereof.

Examples of such organic polymer materials include polyolefines such aspolyethylene and polypropylene, polyimide, polyamide, polyester,polymethylmethacrylate (PMMA), polyphenylenesulfide (PPS),polyethersulfone (PES), epoxy resins, and the like.

F. Metal

Examples of metals include Al, Li, Ti, Mn, In, Sn, Y, La, Ce, Nd, Pr,Gd, Sm, and alloys containing at least one of these metals.

Although the thickness of the separation layer 120 depends uponconditions such as the purpose of exfoliation, the composition of theseparation layer 120, the layer structure, the forming method, etc., thethickness is preferably about 0.5 nm to 20 pm, more preferably about 1nm to 2 μm, most preferably about 5 nm to 1 μm. With the separationlayer 120 having an excessively small thickness, uniformity of filmdeposition deteriorates, thereby causing nonuniformity in exfoliation.With the separation layer 120 having an excessively large thickness, thepower of light (quantity of light) must be increased to ensure goodexfoliating properties of the separation layer 120, and much time isrequired for removing the separation layer 120 later. The thickness ofthe separation layer 120 is preferably as uniform as possible.

The method of forming the separation layer 2 is not limited, and isappropriately selected according to conditions such as the filmcomposition, the thickness, and the like. Examples of the forming methodinclude various vapor phase deposition methods such as CVD (includingMOCVD, low-pressure CVD and ECR-CVD), evaporation, molecular beamevaporation (MB), sputtering, ion plating, PVD, and the like; variousplating methods such as electroplating, immersion plating (dipping),electroless plating, and the like; coating methods such asLangmuir-Blodgett's (LB) technique, spin coating, spray coating, rollcoating, and the like; various printing methods; a transfer method; anink jet method; a powder jet method; and the like. The separation layermay be formed by a combination of at least two of these methods.

For example, where the composition of the separation layer 120 comprisesamorphous silicon (a-Si), the layer is preferably formed by CVD,particularly low-pressure CVD or plasma CVD.

Where the separation layer 120 is made of ceramic by a sol-gel method,or an organic polymer material, it is preferably formed by a coatingmethod, particularly spin coating.

[Step 2]

Next, the transferred layer (thin film device layer) 140 is formed onthe separation layer 120, as shown in FIG. 2.

An enlarged section of portion K (shown by a one-dot chain line in FIG.2) of the thin film device layer 140 is shown on the right side of FIG.2. As shown in FIG. 2, the thin film device layer 140 comprises TFTs(thin film transistor) formed on, for example, an SiO₂ film(intermediate layer) 142, and the TFT comprises source and drain layers146 formed by introducing N-type impurities in a polysilicon layer, achannel layer 144, a gate insulation film 148, a polysilicon gate 150, aprotecting film 154, and an electrode 152 made of, for example,aluminum.

Although, in this embodiment, as the intermediate layer provided incontact with the separation layer 120, the SiO₂ film is used, anotherinsulation film can also be used. The thickness of the SiO₂ film(intermediate layer) is appropriately determined according to thepurpose of forming, the degree of the function exhibited, but thethickness is preferably about 10 nm to 5 μm, more preferably about 40 nmto 1 μm. The intermediate layer is formed for various purposes. Forexample, the intermediate layer is formed for exhibiting at least one ofthe functions as a protection layer for physically or chemicallyprotecting the transferred layer 140, an insulation layer, a conductivelayer, laser light shielding layer, a barrier layer for preventingmigration, and a reflecting layer.

In some cases, the intermediate layer comprising the SiO₂ film or thelike is not formed, and the transferred layer (thin film layer) 140 maybe formed directly on the separation layer 120. An example of cases inwhich the intermediate layer need not be provided is a case in which aTFT in the transferred layer is a bottom gate structure transistor, andno problem with contamination occurs even if the bottom gate is exposedto the surface after transfer.

The transferred layer 140 (thin film device layer) is a layer containingthin film devices such as TFTs or the like, as shown on the right handside of FIG. 2. Besides TFTs, examples of thin film devices include thinfilm diodes and other thin film semiconductor devices, electrodes (forexample, transparent electrodes such as ITO and mesa films), switchingdevices, memory, actuators such as piezoelectric devices, micro mirrors(piezo thin film ceramics), magnetic recording thin film heads, coils,inductors, thin film materials with high permeability and micro magneticdevices comprising a combination of these materials, filters, reflectingfilms, dichroic mirrors, and the like.

Such a thin film device is generally formed through a relatively highprocess temperature in relation to the forming method thereof.Therefore, in this case, the substrate 100 must-resist the processtemperature and have high reliability, as described above.

[Step 3]

Next, the thin film device layer 140 is adhered to a transfer material180 through an adhesive layer 160, as shown in FIG. 3.

Preferable examples of an adhesive which constitutes the adhesive layer160 include various curing adhesives such as reactive curing adhesives,heat curing adhesives, light curing adhesives such as ultraviolet curingadhesives, anaerobic curing adhesives, and the like. As the compositionof the adhesive, any type such as an epoxy type, an acrylate type, or asilicone type, may be used. The adhesive layer 160 is formed by, forexample, the coating method.

In the use of the curing adhesive, for example, the curing adhesive iscoated on the transferred layer (thin film device layer) 140, thetransfer material 180 is adhered to the curing adhesive, and then thecuring adhesive is cured by the curing method according to theproperties of the curing adhesive, to bond and fix the transferred layer(thin film device layer) 140 and the transfer material 180.

Unlike the case shown in the drawing, the adhesive layer 160 may beformed on the transfer material 180 side, and the transferred layer(thin film device layer) 140 may be adhered to the adhesive layer 160.For example, when the transfer material 180 has the adhesive function,the formation of the adhesive layer 160 may be omitted.

Although the transfer material 180 is not limited, a substrate,particularly a transparent substrate can be used. Such a substrate maybe a flat plate or a curved plate. As the transfer material 180, amaterial having heat resistance, corrosion resistance, and the likewhich are poorer than the substrate 100 may be used. The reason for thisis that in the present invention, since the transferred layer (thin filmdevice layer) 140 is formed on the substrate 100 side, and is thentransferred to the transfer material 180, the conditions required forthe transferred layer (thin film device layer) 140, particularly, heatresistance, does not depend upon the temperature conditions in formingthe transferred layer (thin film device layer) 140.

Therefore, when the highest temperature in formation of the transferredlayer 140 is Tmax, as the material for forming the transfer material180, a material having a glass transition point (Tg) or softening pointlower than Tmax can be used. For example, the transfer material 180preferably comprises a material having a glass transition point (Tg) orsoftening point of 800° C. or less, more preferably 500° C. or less,most preferably 320° C. or less.

The transfer material 180 may have as a mechanical property somerigidity (strength), but it may have flexibility and elasticity.

As the material which constitutes the transfer material 180, varioussynthetic resins or various types of glass may be used, particularlyvarious synthetic resins or inexpensive ordinary glass materials (lowmelting point) are preferably used.

Synthetic resins may be either thermoplastic resins or heat curingresins. Examples of such synthetic resins include polyolefins such aspolyethylene, polypropylene, ethylene-propylene copolymers,ethylene-vinyl acetate copolymers (EVA), and the like; cyclicpolyolefins; modified polyolefins; polyvinyl chloride; polyvinylidenechloride; polystyrene; various polyesters such as polamide, polyimide,polycarbonate, poly-(4-methylpentene-1), ionomer, acrylic resins,polymethyl methacrylate, acryl-styrene copolymers (AB resins),butadiene-styrene copolymers, polyolefin copolymers (EVOH), polyetheyeleterephthalate (PET), polubutylene terephthalate (PBT), polycyclohexaneterephthalate (PCT), and the like; polyethers; polyether ketones (PEK);polyether ether ketones (PEKK); polyether imide; polyacetal (POM);polyphenylene oxide; modified polyphenyl oxide; polyacrylate; aromaticpolyetsers (liquid crystal polymers); polytetrafluoroethene;polyvinylene fluoride; other fluororesins; various thermoplasticelastomers of styrene, polyolefin, polyvinyl chloride, polyurethane,fluororubber, chlorinated polyethylene, and the like; epoxy resins;phenolic resins; urea resins; melamine resins; unsaturated polyesters;silicone resins; polyurethane; and copolymers, blends and polymer alloysmainly consisting of these polymers; the like. These polymers may beused singly or in combination of at least two of them (for example, as alaminate of at least two layers).

Examples of glass materials include silicate glass (quartz glass),alkali silicate glass, soda-lime glass, potash lime glass, lead (alkali)glass, barium glass, borosilicate glass, and the like. Of these types ofglass, glass other than silicate glass is preferable because it has amelting point lower than silicate glass, is relatively easily formed andprocessed, and inexpensive.

When a member made of a synthetic resin is used as the transfer material180, there are various advantages that the large transfer material 180can be integrally formed, the member having a complicated shape such asa curved surface or an unevenness can easily be produced, and thematerial cost and production cost are low. Therefore, the use of asynthetic resin is advantageous for producing a large low-priced device(for example, a liquid crystal display).

The transfer material 180 may comprise an independent device, such as aliquid crystal cell, or a portion of a device, such as a color filter,an electrode layer, a dielectric layer, an insulation layer or asemiconductor device.

The transfer material 180 may be made of a material such as a metal,ceramic, a stone material, wood paper, or the like, or may comprise anydesired surface which constitutes a product (a surface of a watch, asurface on an air conditioner, a surface of a printed board, or thelike), or a surface of a structure, such as a wall, a column, a ceiling,a window glass, or the like.

[Step 4]

Next, the substrate 100 is irradiated with light from the back thereof,as shown in FIG. 4.

The light passes through the substrate 100 and is then applied to theseparation layer 120. This causes internal exfoliation and/orinterfacial exfoliation in the separation layer 120, thereby decreasingor eliminating the adhering strength.

The principle of occurrence of internal exfoliation and/or interfacialexfoliation in the separation layer 120 is thought to be based onablation occurring in the constituent material of the separation layer120, discharge of gases contained in the separation layer 120 and aphase change such as melting or vaporization caused immediately afterirradiation.

The ablation means that a solid material (the constituent material ofthe separation layer 120) which absorbs light is photochemically orthermally excited to discharge atoms or molecules due to cutting ofbonds in the surface and inside of the material. This mainly occurs asthe phenomenon that a phase change such as melting, vaporization(evaporation) or the like occurs in the whole or part of the constituentmaterial of the separation layer 120. Also, in some cases, the phasechange causes a fine foam state, and decreases the adhering strength.

The type of the exfoliation produced in the separation layer 120, i.e.,internal exfoliation, interfacial exfoliation or both types ofexfoliation, depends upon the composition of the separation layer 120,and other various factors. One of the factors is the type, wavelength,strength, arrival depth and the like of irradiating light.

As the irradiating light, any light can be used as long as it generatesinternal exfoliation and/or interfacial exfoliation in the separationlayer 120. Examples of the irradiating light include X-rays, ultravioletrays, visible light, infrared light (heat rays), laser light, millimeterwaves, microwaves, electron rays, radiation (α-rays, β-rays and γ-rays),and the like. Of these types of light, laser light is preferable fromthe viewpoint that exfoliation (ablation) is easily produced in theseparation layer 120.

As a laser device for generating laser light, various gas lasers, solidlasers (semiconductor lasers), and the like can be used. However, aneximer laser, an Nd-YAG laser, an Ar laser, a CO₂ laser, a CO laser, anHe—Ne laser and the like are preferably used, and an eximer laser isparticularly preferable.

Since the eximer laser outputs high energy in a short wavelength region,it can generate ablation in the separation layer 120 within a very shorttime, and thus peel off the separation layer 120 with hardly producing atemperature rise in the transfer material 180 and the substrate 100adjacent to the separation layer 120, i.e., with producing neitherdeterioration nor damage.

In producing ablation in the separation layer 120, the wavelength of theirradiating laser light is preferably about 100 to 350 nm. In regard tothe transmittance of the substrate 100 for the light wavelength, thesubstrate 100 has the property that transmittance for a wavelength of250 nm rapidly increases. In this case, irradiation is performed withlight at a wavelength over 300 nm (for example, Xe—Cl eximer laser lightwith 308 nm).

For example, when a phase change such as gas discharge, evaporation orsublimation is generated in the separation layer 120 to provide aseparation property, the wavelength of the irradiating laser light ispreferably about 350 to 1200 nm.

The energy density of the irradiating laser light, particularly theenergy density of eximer laser, is preferably about 10 to 5000 mJ/cm²,more preferably about 100 to 500 mJ/cm². The irradiation time ispreferably about 1 to 1000 nsec, more preferably about 10 to 100 nsec.With a low energy density or a short irradiation time, sufficientablation does not occur, and with a high energy density or a longirradiation time, the irradiating light transmitted through theseparation layer 120 might produce adverse effects on the transferredlayer 140.

As a measure against the adverse effects caused by arrival of theirradiating light transmitted through the separation layer at thetransferred layer 140, for example, a metal film of tantalum (Ta) or thelike is formed on the separation layer (laser absorbing layer) 120. Thiscauses the laser light transmitted through the separation layer 120 tobe totally reflected by the interface of the metal film, thereby causingno adverse effect on the thin film element provided thereon.

Irradiation is preferably performed with the irradiating light,typically laser light, so that the strength is made uniform. Theirradiation direction of the irradiating light is not limited to thedirection perpendicular to the separation layer 120, and the irradiationdirection may be a direction at a predetermined angle with respect tothe separation layer 120.

Where the area of the separation layer 120 is larger than theirradiation area of the irradiating light in one irradiation, the totalregion of the separation layer 120 can be irradiated several times withthe irradiating light. The same position may be irradiated two times ormore, or the same region or different regions may be irradiated withdifferent types of irradiating light (laser light) or irradiating lightat different wavelengths (wavelength ranges).

Next, as shown in FIG. 5, force is applied to the substrate 100 toseparate the substrate 100 from the separation layer 120. Although notshown in FIG. 5, the separation layer sometimes adheres to the substrate100 after separation.

Next, as shown in FIG. 6, the remaining separation layer 120 is removedby, for example, washing, etching, ashing, polishing or a combinationthereof. As a result, the transferred layer (thin film device layer) 140is transferred to the transfer material 180.

When part of the separation layer also adheres to the separatedsubstrate 100, it is removed by the same method as described above. Whenthe substrate 100 is made of an expensive material such as quartz glassor a rare material, the substrate is preferably recycled. Namely, thepresent invention can be applied to the substrate 100, which is desiredto be recycled, with high availability.

The transferred layer (thin film device layer) 140 is completelytransferred to the transfer material 180 through the above steps. Thenthe SiO₂ film adjacent to the transferred layer (thin film device layer)140 may be removed. and a desired protecting film may be formed.

In the present invention, since the transferred layer (thin film devicelayer) 140, which is a layer to be exfoliated, is not directlyexfoliated, but exfoliated through the separation layer adhered thereto,the transferred layer 140 can easily, securely and uniformly beexfoliated (transferred) regardless of the properties of the layer to beexfoliated (the transferred layer 140), and conditions, etc., withoutdamage to the layer to be exfoliated (the transferred layer 140) due tothe exfoliating operation. Therefore, it is possible to maintain thehigh reliability of the transferred layer 140.

The device transfer technique is summarized above.

Next, an example of the method of manufacturing a liquid crystal displaydevice using the above device transfer technique is described.

(First embodiment)

In this embodiment, an example of the process for manufacturing anactive matrix type liquid crystal display device comprising an activematrix substrate, as shown in FIGS. 7, 8 and 9, using the thin filmdevice transfer technique is described.

(Configuration of liquid crystal display device)

As shown in FIG. 7, an active matrix type liquid crystal display devicecomprises backlights 400, a polarizer 420, an active matrix substrate440, a liquid crystal 460, an opposite substrate 480, and a polarizer500. In the present invention, when a flexible substrate is used as eachof the active matrix substrate 440 and the opposite substrate 480, alightweight active matrix type liquid crystal panel having flexibilityand resistance to shock can be realized as a reflective liquid crystalpanel by using a reflecting plate in place of the illumination lightsources 400.

The active matrix substrate 440 used in this embodiment is an activematrix substrate with a built-in driver in which TFTs are arranged in apixel portion 442, and a driver circuit (a scanning line driver and dataline driver 444) is provided.

Namely, as shown in FIG. 8, the pixel portion 442 on the active matrixsubstrate 440 comprises a plurality of TFTs (M1) in which gates areconnected to scanning lines S1, and ends (terminals) are connected todata lines D1, the other ends being connected to the liquid crystal 460.Similarly, the driver portion 444 also comprises TFT (M2).

FIG. 9 is a sectional view showing a principal portion of the activematrix type liquid crystal display device. As shown in the left side ofFIG. 9, the TFT (M1) in the pixel portion 442 comprises source-drainlayers 1100a and 1100b, a gate insulation film 1200a, a gate electrode1300a, an insulation film 1500, and source-drain electrodes 1400a and1400b. Reference numeral 1700 denotes a pixel electrode comprising anITO film or a metallic film. With the ITO film, a transmissive liquidcrystal panel is formed, and with the metallic film, a reflective liquidcrystal panel is formed.

Reference numeral 1702 denotes a region (voltage applied region) where avoltage is applied to the liquid crystal 460 from the pixel electrode1700.

Also, as shown on the right hand side of FIG. 9, the TFT (M2) whichconstitutes the driver portion 444 comprises source-drain layers 1100cand 1100d, a gate insulation film 1200b, a gate electrode 1300b, aninterlayer insulation film 1500, and source-drain electrodes 1400c and1400d.

In FIG. 9, reference numeral 480 denotes, for example, an oppositesubstrate (for example, a soda glass substrate), and reference numeral482 denotes a common electrode.

Reference numeral 1000 denotes a underlying SiO₂ film corresponding toan “intermediate layer”. Reference numeral 1600 denotes an insulationfilm (for example, a CVD SiO₂ film), and reference numeral 1800 denotesan adhesive layer. Reference numeral 1900 denotes a substrate (transfermaterial) comprising, for example, soda glass.

In this embodiment, attention should be given to the point that a recess(through hole) is selectively formed in the insulation film 1600 and theunderlying SiO₂ film, and the pixel electrode 1700 is bent downwardalong the surface of the recess and has the exposed back at the bottomthereof to form the voltage applied region 1702 for the liquid crystal460. This eliminates interposition of the insulation films (theunderlying SiO₂ film (intermediate layer) 1000 and the interlayerinsulation film 1500) between the pixel electrode 1700 and the liquidcrystal layer 460, thereby preventing a voltage loss.

If the insulation films remain on the pixel electrode without causing aproblem in driving the liquid crystal, the insulation films need not becompletely removed. For example, although, in FIG. 9, the underlyingSiO₂ film (intermediate layer) 1000 is completely removed from theregion 1702, the underlying SiO₂ film (intermediate layer) 1000remaining unremoved causes no problem as long as it is thin and causes alittle voltage loss.

A detailed description will now be made.

In this embodiment, the active matrix substrate is manufactured bytransferring, to a desired transfer material, thin film transistors andpixel electrodes which are formed on the predetermined substrate. Inthis case, the device transferred onto the transfer material is reverseto a normal device. As a result, in the transferred device, the pixelelectrode is covered with an insulator film in the state before transfersuch as the interlayer insulation film or the like.

In this state, in assembly of a liquid crystal display device (liquidcrystal panel), the insulator layer is interposed between the pixelelectrode and the liquid crystal layer, and thus a voltage loss in thisportion cannot be neglected.

Therefore, in manufacturing the active matrix substrate, a method isused in which in forming the thin film transistor and the pixelelectrode on the original substrate before transfer, at least a portionof the insulator layer such as the interlayer insulation film or thelike, which causes a problem in the later steps, is previously removedbefore the pixel electrode is formed. This causes a portion of the pixelelectrode to appear in the surface or the vicinity of the surface byseparating the original substrate after the device is transferred to thetransfer material. It is thus possible to apply a voltage from thisportion. Therefore, the above-described trouble (voltage loss) does notoccur.

Even if an unnecessary insulation film remains on the pixel electrodeafter the thin film transistor is transferred, the remaining insulatingfilm is removed in another step, thereby causing no problem.

FIG. 9 shows a liquid crystal display device manufactured by using theactive matrix substrate produced by the above method. [Process formanufacturing liquid crystal display device]

The process for manufacturing the principal portion of the liquidcrystal display device shown in FIG. 9 is described below with referenceto FIGS. 10 to 14.

First, as shown in FIG. 10, TFT (M1, M2) are formed on a substrate (forexample, a quartz substrate) 3000 having high reliability andtransmitting laser light through the manufacturing process shown inFIGS. 1 and 2, and an insulation film 1600 is formed. In FIG. 10,reference numeral 3100 denotes a separation layer (laser absorbinglayer) comprising, for example, amorphous silicon. Reference numerals1400a and 1400b denote electrodes (transistor electrodes) made of, forexample, aluminum which are connected to n⁺ layers 1100a and 1100b,respectively, which constitute the TFT of the pixel portion.

In FIG. 10, both TFTs (M1, M2) are N-type MOSFET. However, the TFT isnot limited to this, p-type MOSFET and CMOS structures may be used.

Next, as shown in FIG. 11, the insulation film 1600 is selectivelyetched to form a contact hole (opening) 1620, and the insulation film1600 and the underlying SiO₂ film 1000 are selectively etched to form anopening (through hole) 1610.

These two openings (1610 and 1620) are simultaneously formed in a commonetching step. Namely, in forming the contact hole 1620 for connectingthe pixel electrode to TFT, the insulation film 1600 and the underlyingSiO₂ film (intermediate layer) 1000 are also selectively removed.Therefore, the special step for forming the opening 1610 is unnecessary,and an increase in the number of the manufacturing steps can thus beprevented.

Although, in FIG. 11, the insulation 1600 and the underlying SiO₂ film(intermediate layer) 1000 are completely removed when the opening 1610is formed, these films may be left as long as a sufficient voltage canbe applied to the liquid crystal. For example, the underlying SiO₂ film(intermediate layer) 1000 may be left.

Even when the insulation film 1600 and the underlying SiO₂ film(intermediate layer) 1000 are completely removed in formation of theopening 1610, a method may be used in which these films are not removedat a time in this step, but these films are partially left in this step,and the films remaining on the pixel electrode are removed in a laterstep (for example, the step after the thin film transistor istransferred) to expose the surface of the pixel electrode.

Next, as shown in FIG. 12, the pixel electrode 1700 made of an ITO filmis formed.

Next, as shown in FIG. 13, a substrate 1900 (transfer material) isadhered through an adhesive layer 1800. Next, as shown in FIG. 13, thesubstrate 3000 is irradiated with eximer laser light from the backthereof, and then is exfoliated.

Next, the separation layer (laser absorbing layer) 3100 is removed tocomplete the active matrix substrate shown in FIG. 14. The bottom (theregion 1702) of the pixel electrode 1700 is exposed to permitapplication of a sufficient voltage to the liquid crystal.

Then an alignment film is formed on the inner sides of the oppositesubstrate 480 and the active matrix substrate 440 shown in FIG. 14,followed by rubbing. Both substrates are then adhered with a sealingagent with a space formed therebetween, and a liquid crystal is sealedin between the both substrates to complete the liquid crystal displaydevice shown in FIG. 9.

Although the above description is made on the basis of a devicestructure (the pixel electrode is in an upper layer, and the transistorelectrode is in a lower layer) in which the transistors electrode layers1400a and 1400b connected to the n⁺ layers 1100a and 1100b,respectively, which constitute the pixel TFT, are in a layer differentfrom the pixel electrode 1700, the device structure is not limited tothis. As shown in FIGS. 15 to 17, even when the pixel electrode and thetransistor electrode are in the same layer, the above manufacturingmethod can be applied.

Namely, as shown in FIG. 15, an opening 1612 is formed at the same timethat electrode contact holes 1622 and 1630 of the TFT are formed.Therefore, the special step for forming the opening 1612 is unnecessary.

Although, in FIG. 15, the interlayer insulation film 1500 and theunderlying SiO₂ film (intermediate layer) 1000 are completely removedwhen the opening 1612 is formed, these films may be left as long as asufficient voltage can be applied to the liquid crystal. For example,the underlying SiO₂ film (intermediate layer) 1000 may be left.

Even when the interlayer insulation film 1500 and the underlying SiO₂film (intermediate layer) 1000 are completely removed in formation ofthe opening 1612, a method may be used in which these films are notremoved at a time in this step, but these films are partially left inthis step, and the films remaining on the pixel electrode are removed ina later step (for example, the step after the thin film transistor istransferred) to expose the surface of the pixel electrode.

Next, as shown in FIG. 16, an aluminum electrode 1402 and a pixelelectrode (ITO) 1702 are formed.

Then, like in the case shown in FIGS. 13 and 14, the thin filmtransistor and pixel electrode are adhered to a transfer material 1900through an adhesive layer 1800, and the substrate 3000 is separatedafter light irradiation to complete the active matrix substrate shown inFIG. 17.

(Second embodiment)

FIGS. 18 and 19 are sectional views showing a device in accordance witha second embodiment of the present invention.

This embodiment is characterized in that the step of forming a colorfilter and a light shielding film (for example, a black matrix) is addedafter the step of forming the pixel electrode made of ITO or a metal toform an active matrix substrate with the color filter and the lightshielding film (for example, a black matrix).

The case where the black matrix is used as the light shielding film isdescribed below.

As the structure of an ordinary thin film transistor, a structure inwhich the color filter and the black matrix are formed on the pixelelectrode cannot be used because the liquid crystal layer and the pixelelectrode are separated.

However, in the present invention, a device is reverse to a normaldevice due to transfer, and thus the contact region between the pixelelectrode and the liquid crystal layer is formed on the side (i.e., theTFT side) opposite to a conventional device.

Therefore, in the original substrate before transfer, the color filterand the black matrix can be formed without any trouble. In this case,only the common electrode is formed on the opposite substrate, and thecolor filter and the black matrix, which are conventionally formed onthe opposite substrate side, need not be strictly aligned with the pixelelectrode, thereby causing the special effect of facilitating assemblyof a liquid crystal display device.

As shown in FIG. 18, a color filter 1770 is formed by a pigmentdispersion method, a dyeing method or an electrodepositon method tocover the principal portion of the pixel electrode 1700, and a lightshielding black matrix 1750 is formed to cover the TFT.

As shown in FIG. 19, the device is adhered to the transfer material 1900through the adhesive layer 1800, and then the substrate 3000 (FIG. 18)is separated to complete an active matrix substrate with the colorfilter and the black matrix.

As described above, when a liquid crystal display device is formed byusing the active matrix substrate, strict alignment with the oppositesubstrate is unnecessary, and assembly is facilitated.

(Third embodiment)

FIG. 20 shows a section of the principal portion of a liquid crystaldisplay device in accordance with a third embodiment of the presentinvention.

The liquid crystal display device shown in FIG. 20 is characterized inthat a terminal (external connection terminal) 1404 (made of ITO or ametal) for connecting a driver IC 4200 is formed on the active matrixsubstrate through the same manufacturing steps as the pixel electrodes.

Namely, in the active matrix substrate, where the external connectionterminal (for example, a terminal for connecting liquid crystal drivingIC) is required, this terminal must be exposed to the surface.

Therefore, in the region where the external connection terminal isprovided, the underlying insulation film (intermediate layer) and theinsulator layer such as interlayer insulation film are moved.

However, the surface of the external connection terminal 1404 need notbe exposed only in the same step as formation of the opening in thepixel electrode region, and another etching step may be added forremoving the film remaining on the surface of the external connectionterminal 1404 in the etching step, to expose the surface.

In FIG. 20, “region P1” is a region (bonding pad) to which the lead 4100of the driver IC 4200 is connected.

Namely, as shown in FIG. 21, the driver IC 4200 is connected to the dataline D1 through the pad P1.

In FIG. 20, the driver IC is a tape carrier package (TCP) type IC, and alead 4100 is connected to the pad P1 (the external connection terminal1404 ) through an anisotropic conductive film (conductive anisotropicadhesive) 4000, the other lead 4104 being connected to a printed board4300 through solder 4004.

In FIG. 20, reference numeral 484 denotes the sealing material(sealant), reference numeral 4102 denotes a tape carrier, and referencenumeral 4002 denotes a conductive filler. Reference numerals 1010 and1012 each denote an alignment film. The same portions as FIG. 9 aredenoted by the same reference numerals.

The process for manufacturing the active matrix substrate shown in FIG.20 is described below with reference to FIGS. 22 to 27. Since themanufacturing process is common to that shown in FIGS. 10 to 14, thesame portions are denoted by the same reference numerals.

First, as shown in FIG. 22, TFT (M1), the data line D1, and the scanningline S1 (not shown in the drawing) are formed on the substrate 3000. InFIG. 22, the pixel portion is shown on the left side, and the terminalportion where the external connection terminal is formed is shown on theright side.

Next, as shown in FIG. 23, the openings 1610 and 1640 are formed at thesame time as the contact holes 1620 and 1630. Therefore, the surface ofthe separation layer 3100 is exposed at the bottoms of the openings 1610and 1640. The special step of forming the openings 1610 and 1640 isunnecessary.

Although, in FIG. 23, the insulation film 1600, the interlayerinsulation film 1500 and the underlying SiO₂ film (intermediate layer)1000 are completely removed when the opening 1610 is formed, these filmsmay partially be left as long as a sufficient voltage can be applied tothe liquid crystal. For example, the underlying SiO₂ film (intermediatelayer) 1000 may be left. However, in the opening 1640, the insulationfilm 1600, the interlayer insulation film 1500 and the underlying SiO₂film (intermediate layer) 1000 must be completely removed by etching inthe same step or another step.

Even when the insulation film 1600, the interlayer insulation film 1500and the underlying SiO₂ film (intermediate layer) 1000 are completelyremoved in formation of the opening 1610 (1640), a method may be used inwhich these films are not removed at a time in this step, but thesefilms are partially left in this step, and the films remaining on thepixel electrode are removed in a later step (for example, the step afterthe thin film transistor is transferred) to expose the surface of thepixel electrode.

Next, as shown in FIG. 24, the pixel electrode made of ITO and theexternal connection terminal 1404 made of ITO are simultaneously formed.

Next, as shown in FIG. 25, a device is adhered to the transfer material1900 through the adhesive layer 1800.

Next, as shown in FIG. 26, the substrate 3000 side is irradiated withlaser light to generate ablation in the separation layer 3100.

Next, the substrate 3000 is separated, and the separation layer 3100 iscompletely removed to form the active matrix substrate shown in FIG. 27.In FIG. 27, reference numeral 1710 denotes a voltage applied region forthe liquid crystal, and region P1 corresponds to a pad for connectingthe region P1 and the driver IC.

Although the above description is made on the basis of a devicestructure (the pixel electrode and the external connection terminal arein an upper layer, and the transistor electrodes are in a lower layer)in which the transistor electrode layers 1400a and 1400b connected tothe n⁺ layers 1100a and 1100b, respectively, which constitute the TFT ofthe pixel, are in a layer different from the pixel electrode 1700 andthe external connection terminal 1404, the device structure is notlimited to this. As shown in FIGS. 28 to 30, even when the pixelelectrode, the external connection terminal and the transistor electrodeare in the same layer, the above manufacturing method can be applied.

Namely, as shown in FIG. 28, openings 1612 and 1642 are formed at thesame time as electrode contact holes 1622 and 1630 of the TFT.Therefore, the special step for forming the openings 1612 and 1642 isunnecessary.

Next, as shown in FIG. 29, an aluminum electrode 1402, the data line D1(and the scanning line not shown in the drawing) made of aluminum, apixel electrode (ITO) 1702 made of ITO and an external connectionterminal 1406 made of ITO are formed.

Then, the device is adhered to the transfer material 1900 through theadhesive layer 1800, and the substrate is separated after lightirradiation to complete the active matrix substrate shown in FIG. 30.

The pixel electrode and the external connection terminal need not bemade of ITO, and may be a metal electrode made of aluminum which serveas a reflection type pixel electrode. When the pixel electrode is ametal electrode, there is the advantage of low wiring resistance. Inthis case, the external connection terminal is made of the same metalmaterial, thereby causing an advantage from the viewpoint of electricalproperties.

(Fourth embodiment)

FIGS. 31 to 38 shows the sectional structure of a device in accordancewith a fourth embodiment of the present invention.

Although, in the above embodiments, the insulator layer below the pixelelectrode is previously removed before transfer of the device, in thisembodiment, at least a portion of the insulator layer below the pixelelectrode is removed in self alignment by using a black matrix aftertransfer.

Namely, the black matrix is formed on the original substrate beforetransfer, and exposure is performed by using the black matrix as anexposure mask after transfer by utilizing the fact that the black matrixis formed around the pixel electrode, followed by development to form adesired resist pattern. The insulator layer below the pixel electrode isremoved by using the resist pattern as an etching mask.

A detailed description will now be made.

First, as shown in FIG. 31, like in FIG. 10, TFT (M1) is formed, theinsulation film 1600 is then formed to cover the TFT (M1), a contacthole is formed in the insulation film 1600, and then a pixel electrode(an ITO film or metal film) 1790 is formed. In this embodiment,attention should be given to the point that unlike FIGS. 11 and 15, noadditional opening is formed in the insulation film 1600.

Next, a black matrix 1750 is formed. The black matrix 1750 is providedto shield the periphery of the principal portion (the voltage appliedregion for the liquid crystal) from light except the principal portion,as shown on the lower side of FIG. 34.

Next, as shown in FIG. 32, a device is adhered to the transfer material1900 through the adhesive layer 1800, and the substrate 3000 side isirradiated with laser light.

Next, as shown in FIG. 33, the substrate 3000 is separated, and theremaining separation layer 3100 is also removed.

Next, as shown in FIG. 34, a photoresist 5000 is formed on the surfaceobtained by separating the substrate 3000, followed by exposure from thetransfer material 1900 side. In this case, the black matrix 1750 servesas an exposure mask to automatically irradiate only the region ofcontact between the pixel electrode and the liquid crystal with light.

Next, as shown in FIG. 35, the photoresist 5000 is patterned bydevelopment.

Next, as shown in FIG. 36, the underlying insulation film (intermediatelayer) 1000, the gate insulation film 1500, the insulation film 1600 areetched by using the patterned photoresist 5000 as a mask to form anopening 8002. As a result, the surface of the pixel electrode isexposed.

Like in the above embodiments, the films may be left on the pixelelectrode as long as no trouble occurs in driving the liquid crystal.Alternatively, the remaining films may be removed in another step toexpose the surface of the pixel electrode.

Next, as shown in FIG. 37, the photoresist 5000 is removed to completean active matrix substrate.

The liquid crystal display device shown in FIG. 38 is manufactured byusing the active matrix substrate. In FIG. 38, the same portions as FIG.9 are denoted by the same reference numerals.

Although, in this embodiment, only the black matrix is formed, the colorfilter may be formed on the active matrix substrate as long as theexposure conditions for photoresist are satisfied, as in the case shownin FIGS. 18 and 19.

Like in the above embodiments, not only the pixel electrode but also theexternal connection terminal can be formed by the same method asdescribed above.

(Fifth embodiment)

FIGS. 39 to 42 show the sectional structure of a device in accordancewith a fifth embodiment of the present invention.

In this embodiment, when a thin film transistor is formed on an originalsubstrate before transfer, a pixel electrode is previously formed.Therefore, the original substrate before transfer is separated aftertransfer of the device to automatically expose the surface of the pixelelectrode.

Namely, as shown in FIG. 39, an aluminum electrode 7100 and a pixelelectrode 7000 made of ITO are formed on a separation layer 3100. Thepixel electrode 7000 may be made of a metal such as aluminum or thelike. In this case, the pixel electrode 7000 can be formed at the sametime as the aluminum electrode 7100.

Next, as shown in FIG. 40, an interlayer insulation film 7200,source-drain layers 7300a and 7300b, a gate insulation film 7400, and agate electrode 7500 are formed, and the device is then adhered to atransfer material 7700 through an adhesive layer 7600. Next, thesubstrate 3000 side is irradiated with laser light.

Next, as shown in FIG. 41, the substrate 3000 is separated, and theremaining separation layer 3100 is removed to complete an active matrixsubstrate.

The liquid crystal display device shown in FIG. 42 is manufactured byusing the active matrix substrate. In FIG. 42, the same portions as FIG.9 are denoted by the same reference numerals.

In FIG. 42, reference numeral 4100 denotes a lead of a driver IC;reference numeral 4102, a tape carrier; reference numeral 4000, aconductive anisotropic adhesive; and reference numeral 4002, aconductive filler.

As described above, the present invention is capable of effectivelyremoving the problems due to reversal of a device which results from theuse of the transfer technique. Therefore, a substrate used inmanufacturing thin film devices and a substrate (for example, asubstrate having preferable properties from the viewpoint of applicationof a product) used in, for example, actual use of a product can befreely individually selected. For example, an active matrix substratecan be formed by using a flexible plastic substrate.

The active matrix substrate can be used for not only a liquid crystaldisplay device but for also other applications. For example, an activematrix substrate on which an electronic circuit (a computer or the like)comprising TFTs is mounted can be formed.

The present invention is not limited to the above embodiments, andvarious modifications can be made. For example, although, in each of theabove embodiments, a type (top gate type) in which a gate electrode isdisposed above a channel after the channel is formed is described as anexample of thin film transistor (TFT) structures, TFT structures of atype (bottom gate type) in which the gate electrode is formed before thechannel is formed can also be used.

Further, although, in the embodiments, the manufacturing substrate isseparated from the separation layer by irradiation with laser light orthe like, of course, the present invention can be applied to any casesusing other methods of separating the substrate as long as the methodscan separate the manufacturing substrate from the separation layer.

Industrial Applicability

As described above, the present invention is capable of forming a liquidcrystal display device by forming the thin film transistors on thesubstrate and then transferring thin film transistors to any one ofvarious other substrates, thus providing as an active type liquidcrystal display device a liquid crystal display device using glass,plastic, films or the like, which cannot be used for conventional activetype liquid crystal display devices.

1. A method of manufacturing an active matrix substrate comprising apixel portion including thin film transistors connected to scanninglines and signal lines arranged in a matrix, and pixel electrodesconnected to terminals of the thin film transistors, the methodcomprising the steps of: forming a separation layer on a substrate;forming the thin film transistors over the separation layer; forming aninsulation film on the thin film transistors and over the separationlayer; selectively removing at least a portion of the insulation filmwhere each of the pixel electrodes is to be formed; forming each of thepixel electrodes on the insulation film and the separation layer in theregion where at least a portion of the insulation film has been removed;adhering the thin film transistors to a transfer material with anadhesive layer; producing exfoliation in the separation layer and/or atan interface of the separation layer and the substrate to separate thesubstrate from the separation layer; and removing any portion of theseparation layer remaining on the pixel electrodes to form an activematrix substrate using the transfer material as a new substrate.
 2. Themethod of manufacturing an active matrix substrate according to claim 1,wherein the step of selectively removing at least a portion of theinsulation film comprises forming contact holes for electricallyconnecting the pixel electrodes to the thin film transistors.
 3. Themethod of manufacturing an active matrix substrate according to claim 2,further comprising connecting the pixel electrodes directly to animpurity layer which constitutes the thin film transistors.
 4. Themethod of manufacturing an active matrix substrate according to claim 2,further comprising the steps of: forming electrodes connected to animpurity layer which constitutes the thin film transistors; andconnecting the pixel electrodes to the corresponding electrodesconnected to the impurity layers.
 5. The method of manufacturing anactive matrix substrate according to claim 1, further comprising thestep of forming at least one of a color filter and a light shieldingfilm after the step of forming the pixel electrodes.
 6. The method ofmanufacturing an active matrix substrate according to claim 1, whereinin selectively removing at least a portion of the insulation film, atleast a portion of the insulation film is selectively removed from aregion where an external connection terminal is to be provided.
 7. Themethod of manufacturing an active matrix substrate according to claim 6,further comprising the step of forming the external connection terminalas a conductive layer made of a same material as the pixel electrodes ora same material as an electrode connected to an impurity layer whichconstitutes the thin film transistors.
 8. A method of manufacturing anactive matrix substrate comprising a pixel portion including thin filmtransistors connected to scanning lines and signal lines arranged in amatrix, and pixel electrodes connected to terminals of the thin filmtransistors, the method comprising the steps of: forming a separationlayer on a substrate; forming an intermediate layer on the separationlayer; forming the thin film transistors on the intermediate layer;forming an insulation film on the thin film transistors and theintermediate layer; selectively removing at least a portion of theinsulation film where each of the pixel electrodes is to be formed;forming each of the pixel electrodes on the insulation film and theseparation layer in the region where at least a portion of theinsulation film is removed; adhering the thin film transistors to atransfer material with an adhesive layer; producing exfoliation in theseparation layer and/or at an interface of the separation layer and thesubstrate to separate the substrate from the separation layer; andremoving any portion of the separation layer remaining on theintermediate layer and the pixel electrodes to form an active matrixsubstrate using the transfer material as a new substrate.
 9. The methodof manufacturing an active matrix substrate according to claim 8,wherein the step of selectively removing at least a portion of theinsulation film comprises forming contact holes for electricallyconnecting the pixel electrodes to the thin film transistors.
 10. Themethod of manufacturing an active matrix substrate according to claim 9,further comprising connecting the pixel electrodes directly to animpurity layer which constitutes the thin film transistors.
 11. Themethod of manufacturing an active matrix substrate according to claim 9,further comprising the steps of: forming electrodes connected to animpurity layer which constitutes the thin film transistors; andconnecting the pixel electrodes to the corresponding electrodesconnected to the impurity layers.
 12. The method of manufacturing anactive matrix substrate according to claim 8, further comprising thestep of forming at least one of a color filter and a light shieldingfilm after the step of forming the pixel electrodes.
 13. The method ofmanufacturing an active matrix substrate according to claim 8, whereinin selectively removing at least a portion of the insulation film, atleast a portion of the insulation film is selectively removed from aregion where an external connection terminal is to be provided.
 14. Themethod of manufacturing an active matrix substrate according to claim13, further comprising the step of forming the external connectionterminal as a conductive layer made of a same material as the pixelelectrodes or a same material as an electrode connected to an impuritylayer which constitutes the thin film transistors.
 15. A method ofmanufacturing an active matrix substrate comprising a pixel portionincluding thin film transistors connected to scanning lines and signallines arranged in a matrix, and pixel electrodes connected to terminalsof the thin film transistors, the method comprising the steps of:forming a separation layer on a transmissive substrate; forming the thinfilm transistors over the separation layer or on an intermediate layerformed on the separation layer; forming an insulation film on the thinfilm transistors; forming the pixel electrodes made of a conductivematerial on the insulation film; forming a light shielding layer that isoverlapped with the thin film transistors, and not overlapped with atleast a portion of the pixel electrodes; adhering the thin filmtransistors and the light shielding layer to a transmissive transfermaterial with a transmissive adhesive layer; irradiating the separationlayer through the transmissive substrate to produce exfoliation in theseparation layer and/or at an interface of the separation layer and thetransmissive substrate to separate the transmissive substrate from theseparation layer; forming a photoresist on a surface obtained byseparating the transmissive substrate or the surface of a layerappearing after removing any remaining portion of the separation layer;irradiating light to expose only a predetermined portion of thephotoresist using the light shielding layer as a mask, followed bydevelopment to form a desired photoresist mask; selectively removing atleast a portion of the intermediate layer and the insulation film or atleast a portion of the insulation film by using the photoresist mask;and removing the photoresist mask to form an active matrix substrateusing the transfer material as a new substrate.
 16. A method ofmanufacturing an active matrix substrate comprising a pixel portionincluding thin film transistors connected to scanning lines and signallines arranged in a matrix, and pixel electrodes connected to terminalsof the thin film transistors, the method comprising the steps of:forming a separation layer on a substrate; forming the pixel electrodesover the separation layer or on an intermediate layer formed on theseparation layer; forming an insulation film on the pixel electrodes,and forming the thin film transistors on the insulation film torespectively connect the thin film transistors to the pixel electrodes;adhering the thin film transistors to a transmissive transfer materialwith a transmissive adhesive layer; producing exfoliation in theseparation layer and/or at an interface of the separation layer and thesubstrate to separate the substrate from the separation layer; andremoving any portion of the separation layer remaining on theintermediate layer to form an active matrix substrate using the transfermaterial as a new substrate.
 17. The method of manufacturing an activematrix substrate according to claim 16, further comprising forming aconductive material layer on the separation layer or on the intermediatelayer at a position where an external connection terminal is to beformed.
 18. An active matrix substrate manufactured by the method ofmanufacturing an active matrix substrate according to claim
 1. 19. Anactive matrix substrate manufactured by the method of manufacturing anactive matrix substrate according to claim
 8. 20. An active matrixsubstrate manufactured by the method of manufacturing an active matrixsubstrate according to claim
 15. 21. An active matrix substratemanufactured by the method of manufacturing an active matrix substrateaccording to claim
 16. 22. A liquid crystal display device comprising anactive matrix substrate manufactured by the method of manufacturing anactive matrix substrate according to claim
 1. 23. A liquid crystaldisplay device comprising an active matrix substrate manufactured by themethod of manufacturing an active matrix substrate according to claim 8.24. A liquid crystal display device comprising an active matrixsubstrate manufactured by the method of manufacturing an active matrixsubstrate according to claim
 15. 25. A liquid crystal display devicecomprising an active matrix substrate manufactured by the method ofmanufacturing an active matrix substrate according to claim
 16. 26. Adevice comprising: a substrate; an adherent layer formed over thesubstrate; a thin film device being attached to the substrate by theadherent layer; at least one of an insulation film, which is positionedover the thin film device with respect to the adherent layer, and anintermediate layer, which is positioned between the thin film device andthe adherent layer, the one of the insulation film and the intermediatelayer having an opening where no thin film device is formed; and a pixelelectrode connected with the thin film device, the pixel electrode beingpositioned over the adherent layer and substantially exposed through theopening.
 27. A device according to claim 26, wherein a contact hole isprovided in the intermediate layer and the pixel electrode is connectedwith the thin film device through the contact hole.
 28. A deviceaccording to claim 26, further comprising an other electrode exposedthrough an other opening in the at least one of the insulating film andthe intermediate layer, the other electrode including an externalconnection terminal that connects with an external circuit.
 29. A deviceaccording to claim 26, wherein the thin film device is selected from thegroup including a thin film transistor (TFT), a thin film diode, anelectrode, a switching device, a memory, an actuator, magnetic recordingthin film head, a coil, an inductor, a filter, a reflector, dichroicmirror and combination thereof.
 30. A device according to claim 26,further comprising a light shielding layer being positioned over thethin film device.
 31. The device according to claim 28, the otherelectrode being electrically connected to the same thin film device asthe pixel electrode.
 32. The device according to claim 28, the pixelelectrode being formed from a substantially transparent electricallyconductive material.
 33. The device according to claim 26, furthercomprising an alignment layer formed over the pixel electrode.